Rotary screen washer

ABSTRACT

Equipment for separating liquids and solids and particularly for separating pulp stock and &#39;&#39;&#39;&#39;water&#39;&#39;&#39;&#39; in the paper industry of the kind having a perforate, inclined cylindrical basket and a screw conveyor moving the materials to be separated along the drum, in which there are sprays directed at the drainage surface of the drum and carried by and rotatable with the screw-type conveyor to keep that drainage surface free.

United States Patent 72] Inventor Gilbert L. Bancroft West Vancouver, British Columbia, Canada [21] Appl. No. 828,285

[22] Filed May 27,1969

[45] Patented Nov. 2, 1971 [73] Assignee S. W. Hooper & Co. Ltd.

North Vancouver, British Columbia, Canada [54] ROTARY SCREEN WASHER 10 Claims, 3 Drawing Figs.

[52] U.S.Cl 210/405,

[56] References Cited UNITED STATES PATENTS 1,990,992 2/1935 Lang et al. 210/415 X 3,126,818 3/1964 Koelsch..... 210/415 X 3,188,942 6/1965 Wandel 210/415 X 3,230,865 1/1966 Hibbel et a1. 210/415 X Primary Examiner-Reuben Friedman Attorney- Fetherstonhaugh & Co.

ABSTRACT: Equipment for separating liquids and solids and particularly for separating pulp stock and water" in the paper industry of the kind having a perforate, inclined cylindrical basket and a screw conveyor moving the materials to be separated along the drum, in which there are sprays directed at the drainage surface of the drum and carried by and rotatable with the screw-type conveyor to keep that drainage surface free.

PATENTEnuuv 2 1971 3,616,932

INVENTOA? GIL BERT L. BANCROFT ROTARY SCREEN WASHER I BACKGROUND OF THE INVENTION This invention is concerned with equipment for separating liquids from solids such as for example separating pulp stock and water. It is particularly concerned with such equipment comprising a perforate, cylindrical basket with a screw-type conveyor located within the drum and of approximately similar diameter to the internal diameter of the drum and adapted to move materials to be separated along the drum so that solids are carried through the drum and the liquids drain from it. 7

The drum or drainage basket in the pulp and paper industry is normally constructed of rolled, perforated plate although wire mesh drums or the like could be used when properly supported.

In the pulp and paper industry and, as will be L apparent, in other applications, the efficiency of a separator of this kind is directly related to the cleanliness or freedom of the drainage surface of the drum and this is particularly the case where drainage is by gravity rather than by combination of special vacuum conditions and gravity.

Perhaps the most common of the current methods of preventing blocking of the drainage surface of these drums is to provide on the flights of the screw-type conveyor, wiper blades or brushes. As these blades or brushes rotate with the screw they remove material which might otherwise clog up that surface and impede further drainage. However, these devices wear and so it is necessary that they be adjusted from time to time or be replaced.

Another method which has been proposed is to mount fixed sprays or jets outside the drum to be directed onto the drainage surface of the drum but this is not by any means satisfactory. L

BRIEF SUMMARY OF THE INVENTION The invention provides equipment for separating liquids from solids of the kind comprising a cylindrical perforate drum with a screw-type conveyor located within the drum and adapted to move materials to be separated therealong in which the conveyor carries nozzles from which fluid sprays or jets can be directed outwardly onto the inner surface of the drum. Preferably the nozzles are arranged at or close to the radial extremities of the screw flights and may take the form of a tube secured immediately behind the leading edge of the flights of the conveyor. Alternatively the flights could be hollow or channeled. liquid but in certain applications it is desirable to use for example, steam or compressed air.

DESCRIPTION OF THE DRAWINGS DESCRIPTION OF A PREFERRED EMBODIMENT The embodiment of the invention in the drawings comprises a cylindrical drum 10 which is of rolled perforated or drilled plate, the perforations being indicated by reference numeral ll.

Located axially within the drum is a screw-type conveyor indicated generally at 12 and comprising a central hollow shaft 13 and flights 14. As can be seen in FIG. 2 the peripheries 15 of the flights are of knife edge configuration.

Secured to the flights as for example, by brazing or welding is a tube 16, the tube being secured close to the periphery of the flight so as to be of helical form. LThe tube is provided with holes 17 along its length whichconstitute nozzles andthe nozzles are directed outwardly of the axis of rotation ofthe conveyor i.e. are directed Ltowards the drainage surface of the stationary drum.

The end 18 of the pipe is blocked as by cap 19 and end 20 of the pipe 16 is connected to the shaft 13 by a union 21.

In use, fluid under pressure, usually water in the pulp and paper industry, but either a liquid or a. gas, is supplied to the hollow shaft 13 and from that shaft reaches the pipe 16 to be directed through the nozzle 17 onto the drainage surface of the drum 10.

It will be appreciated that the apparatus is subject L to various modifications which would not deviate from its scope. For example the tube 16 could be replaced! by forming the flights of the screw conveyor of sheet metal to be hollow as is illustrated in FIG. 3 where the flights 30 are formed by two walls 31 and 32 which define a hollow space and there are nozzles 33 at the edges of the flights directed towards the inner surface of the drum. Alternatively the end region of a flight could be turned over to form a channel extending around the edge of the screw. Similarly a conveyor with solid flights could be formed with appropriate bores or passages extending from the shaft to the outer periphery of the flights.

It has been found with the equipment according to this invention that the drainage and separation is very efficient particularly in the paper and pulp industry for separating pulp stock and the water or other liquid even though one is adding extra water.

I claim:

1. Equipment for separating liquids and solids comprising a cylindrical drum defined by a perforate wall, a screwtype conveyor having a central shaft and helical flights thereon, the conveyor being axially rotatable within the drum to convey materials to be separated therealong, the flights having radially outermost helical edges close to the wall of the drum, said conveyor including a plurality of nozzles movable therewith and located close to the radially outermost edges of the flights and directed radially outwards towards the wall of the drum and means connecting the nozzles to a source of fluid under pressure.

2. Equipment as claimed in claim 1 wherein said nozzles are interconnected by a common fluid supply passage.

3. Equipment as claimed in claim 2 wherein said passage is helical and extends around the helical, radially outermost edges of the flights of the conveyor.

4. Equipment as claimed in claim 3 wherein said passage comprises a tube secured close to the helical, radially outermost edges ofthe flights of the conveyor.

5. Equipment as claimed in claim 3 wherein said passage is formed integrally with the flights of the conveyor.

6. Equipment as claimed in claim 2 wherein the flights of the conveyor are of double wall structure, the space between the walls of the flights constituting the fluid supply passage.

7. Equipment as claimed in claim 4 in which said screw-conveyor includes a coaxial fluid supply passage and a terminal portion of the helical fluid supply passage communicates Lwith the coaxial fluid supply passage.

8. Equipment as claimed in claim 1 in which said nozzles are formed in a helical passage extending around the radially outer helical edge of the flights of the conveyor, a main fluid supply passage extends coaxially with the conveyor and a terminal portion of said helical passage communicates with said main passage.

9. Equipment for separating pulp stock and liquid comprising a cylindrical drum defined by a perforate wall, a screwtype conveyor having a central shaft and helical flights thereon, the conveyor being axially rotatable .within the drum to convey pulp stock and liquid therealong, the flights of the conveyor having a diameter only slightly less than the internal diameter of said drum, and a passage extending contiguously with edges of the flights of the conveyor adjacent to the drum, said passage having a plurality of nozzles directed radially out wardly and means for connecting said passage to a source of fluid under pressure, the arrangement being such that fluid passing through the nozzles is directed onto the inner surface of the drum.

of the drum and a fluid-carrying passage contiguous with that radially outermost edge of the flights said passage having nozzles directed radially outwards towards the wall of the drum and means connecting the nozzles to a source of fluid under materials to be separated therealong, the flights of the con- 5 Pressureveyor having radially outermost helical edges close to the wall LII 

1. Equipment for separating liquids and solids comprising a cylindrical drum defined by a perforate wall, a screw-type conveyor having a central shaft and helical flights thereon, the conveyor being axially rotatable within the drum to convey materials to be separated therealong, the flights having radially outermost helical edges close to the wall of the drum, said conveyor including a plurality of nozzles movable therewith and located close to the radially outermost edges of the flights and directed radially outwards towards the wall of the drum and means connecting the nozzles to a source of fluid under pressure.
 2. Equipment as claimed in claim 1 wherein said nozzles are interconnected by a common fluid supply passage.
 3. Equipment as claimed in claim 2 wherein said passage is helical and extends around the helical, radially outermost edges of the flights of the conveyor.
 4. Equipment as claimed in claim 3 wherein said passage comprises a tube secured close to the helical, radially outermost edges of the flights of the conveyor.
 5. Equipment as claimed in claim 3 wherein said passage is formed integrally with the flights of the conveyor.
 6. Equipment as claimed in claim 2 wherein the flights of the conveyor are of double wall structure, the space between the walls of the flights constituting the fluid supply passage.
 7. Equipment as claimed in claim 4 in which said screw-conveyor includes a coaxial fluid supply passage and a terminal portion of the helical fluid supply passage communicates with the coaxial fluid supply passage.
 8. Equipment as claimed in claim 1 in which said nozzles are formed in a helical passage extending around the radially outer helical edge of the flights of the conveyor, a main fluid supply passage extends coaxially with the conveyor and a terminal portion of said helical passage communicates with said main passage.
 9. Equipment for separating pulp stock and liquid comprising a cylindrical drum defined by a perforate wall, a screw-tYpe conveyor having a central shaft and helical flights thereon, the conveyor being axially rotatable within the drum to convey pulp stock and liquid therealong, the flights of the conveyor having a diameter only slightly less than the internal diameter of said drum, and a passage extending contiguously with edges of the flights of the conveyor adjacent to the drum, said passage having a plurality of nozzles directed radially outwardly and means for connecting said passage to a source of fluid under pressure, the arrangement being such that fluid passing through the nozzles is directed onto the inner surface of the drum.
 10. Equipment for separating liquids and solids comprising a cylindrical drum defined by a perforate wall, a screw-type conveyor having a central shaft and helical flights thereon, the conveyor being axially rotatable within the drum to convey materials to be separated therealong, the flights of the conveyor having radially outermost helical edges close to the wall of the drum and a fluid-carrying passage contiguous with that radially outermost edge of the flights said passage having nozzles directed radially outwards towards the wall of the drum and means connecting the nozzles to a source of fluid under pressure. 